Acidemia is a stoner/doom trio from Lages, Santa Catarina, Brazil, formed by Henrique Soares (bass/vocals), Mateus Varela (guitar), and Thiago Granetto (drums), drawing heavily from Electric Wizard and Monolord. Their 2021 album Podridão marked a shift toward compositions entirely in Portuguese, blending sludge-inflected doom with psychedelic heaviness across seven tracks. The band has been featured on the Weedian-curated Trip to Brazil compilation, placing them among the notable voices in Brazil's growing stoner/doom underground.

Acrament was a death metal band from Santiago, Chile, active from the early 1990s until their split. The band's lineup included Christian Asenjo on vocals and guitar, Daniel Muñoz on lead guitar, Dario Díaz on bass, and Luis Pinto on drums. Their 1995 promotional demo "Lands of Blood" stands as their sole documented release.

Acrimonious is a technical death metal band from Concepción, Chile, with roots going back to 1991 under the name Crematory before adopting their current name in 1992. The band released the full-length "Crisis de Odio" in 2005 and the EP "Infierno Terrenal" in 2017, both recorded in Concepción, along with the demo compilation "Unburied Past" in 2020. Their current lineup features Mauricio Cea on vocals, Jorge Matus and Danilo Garcia on guitars, Raúl Seguel on bass, and Patricio Lepe on drums.

Acrostic are a thrash metal band from Viña del Mar who describe their sound as "Noisethrash" — a blend of old-school thrash, hardcore punk, and crust rooted in the Bay Area and European thrash traditions. The trio of Janito Attack, Pablito Attack, and Pelao Attack released their full-length "Sincretismo-Posguerra" in November 2016 on Underground Defenders Records, a 11-track record recorded at JRP Studios in Viña del Mar and limited to 500 copies.

Acrópole is a black metal band from Rio Brilhante and Dourados in Mato Grosso do Sul, active since 2020. Based deep in Brazil's interior rather than in the traditional urban metal centers, the band operates in the raw, atmospheric tradition of Brazilian black metal, contributing to what is a notably sparse but growing extreme metal presence in the Mato Grosso do Sul state.

Acsa is a heavy metal band from Cipolletti, in the Patagonian province of Río Negro, Argentina, formed under their current name around 2014 after originating as Pucara in 2009. The band's lineup of Javier Burgos on vocals, David Ariel Rodríguez on guitar, Damián Zeballos on bass, and Alejandro Rodríguez on drums recorded their debut album "Sangriento Final" at Horus Estudio in Cipolletti in 2021. Their sound draws from the classic Argentine heavy metal tradition while aiming for a heavier, more original direction.

Act of Revenge is a groove/death metal and deathcore band from Salvador, Bahia, formed in 2015 and anchored by vocalist Danfacto Oliveira, whose performance earned the band Best Vocalist honors at the Prêmio Palco do Rock 2014 popular vote — the same year they also won Best Band. Their 2018 EP 5 Atos delivers heavy, groove-driven material entirely in Portuguese, and the band has performed across multiple editions of the Festival Palco do Rock, establishing them as one of Salvador's most visible acts in the heavy underground.

Actum Est is a symphonic black metal band from Belo Horizonte, Minas Gerais, featuring a six-piece lineup that incorporates cello alongside traditional metal instrumentation — a rare texture in Brazil's black metal scene. Formed in 2005 (catalogued under their current activity since 2013), the band released the demo Obscure Symphonies Into the Black Mantle in 2006, channeling themes of occultism and darkness through a lush, orchestrated approach that sets them apart from the rawer strains of the Brazilian underground.

Acutor is a thrash/black metal band from Bogotá, Colombia, formed in 1993 and regarded as a seminal force in the Latin American metal underground. Their 1997 debut album "Dios Ha Muerto" — sung entirely in Spanish with nihilistic and anti-religious lyrics inspired by Nietzschean philosophy — established them as one of the genre's earliest and most distinctive voices on the continent. They have shared stages with major Colombian and international metal acts and remain active on the Viuda Negra Music label.